Well the Duratech 2.3's have signifigantly more pep to them compared to the older ones, though still not exactly a rocket.
any 2.3 and an auto tranny are going to be slow as hell.
Hopefully; since it has the trailer package on it it has a auxiliary trans cooler. That is a BIG thing keeping Ranger auto-trannies alive, make certain it has one and is functional. Even though it's a new truck I'd be tempted to wire in a trans temp gauge to keep an eye on. Seriously, Ford Ranger Auto's can get out of hand and die in a hurry if you're not careful.
My guess would be 2-3,000 lbs. With the 3,000 lb end of the scale being on the shorter trips. Manual trannies are far more forgiving with weight.
It'll probably have an 8.8" out in the rear as well, I've seen an older 2wd 4cyl Ranger with a tow package have that.
If he's hardcore, there is always going to a slightly numerically higher gear ratio, that will take alot of the stress off the tranny as well. The advantage of a 2wd, you only have to do the rear end